The invention relates to endoscopic video cameras having lens assemblies inside a chamber that are axially movable due to the movement of magnets outside of the chamber.
Endoscopes and endoscopic video cameras are now widely used by physicians during surgery to view inside body cavities. Typically, the endoscopic video camera contains an optical focusing lens and a focusing device that can be adjusted to optimize images transmitted by the endoscope. After each use with a patient, the endoscope and endoscopic video camera must be cleaned and sterilized before they can be used again. Typically, sterilization is performed either by high temperature steam autoclaving or by submersion in a sterilizing liquid. Due to cost and time considerations, it is desirable to sterilize both endoscopes and endoscopic video cameras using high temperature steam autoclaving.
One problem with previous endoscopic video camera designs is that direct mechanical linkages used to adjust the position of the lens expose the focusing lens to sterilization fluid, steam or other contaminants. To address this problem endoscopic video cameras have been developed that use lens in hermetically sealed interior chambers and use magnetic drives to move the lens axially within the interior chamber for focusing purposes. Such endoscopic video cameras are described in U.S. Pat. No. 5,359,992 issued to Hori et al., and U.S. Pat. No. 5,056,902 issued to Chinnock et al. In these designs, internal magnets connected to the lens within the interior chamber move in response to the rotation of external magnets located around the periphery of the interior chamber. However, magnet only focusing may not permit sufficient focusing precision and may not have sufficient holding strength to maintain the lens in the optimum focusing position. Further, these prior art designs have mechanical linkages outside the interior chamber that, like the prior art designs, are exposed to sterilization fluid, steam and other contaminants. Additionally, because there is no direct mechanical linkage between the magnets outside the interior chamber and the magnets inside the interior chamber, a drop, sudden shaking or knocking of the device may result in a break down in the magnetic connection between the inner and outer structures and the magnetic connection between the internal and external magnets can be lost permanently.
In an effort to avoid these problems, other endoscopic video camera designs have moved the mechanical linkage inside the sealed chamber. Examples of such designs are U.S. Pat. No. 5,978,161 issued to Lemke (xe2x80x9cLemkexe2x80x9d), U.S. Pat. No. 5,835,865 issued to Speier et al. (xe2x80x9cSpeierxe2x80x9d) and U.S. Pat. No. 5,706,143 issued to Hipp (xe2x80x9cHippxe2x80x9d). However, these designs require machining of lens cells with helical grooves and magnet seats, mechanical linkages to connect the internal magnets to the lens or they require the internal magnet to travel within a helical channel in order to convert the rotational movement of the internal magnets to linear movement of the lens. For example, in Lemke the holder that carries the lens must be machined or formed to have a helical guiding groove and seats for the internal magnet. In Speier, the internal magnets are fixed to a rotatable cylinder having a pin. The rotation of the internal magnets rotates the pin that is mechanically linked to a helical groove formed on the outside diameter of the lens forcing the lens to move axially. In another example, in Hipp, the separate internal magnet is attached to the lens and the magnet must travel within a helical channel formed in a sleeve as the lens rotates.
What is needed therefore is a magnetic focusing device with a simplified design having a sealed cylinder that makes the device easy to operate, eliminates complex mechanical linkages, reduces the amount of machining done to the lens, resists shocks due to dropping or shaking, and permits precision focusing.
Accordingly, it is an object of the invention to provide a device and method using magnetic forces to position and focus a lens within a sealed chamber that does not require a mechanical linkage between the lens and internal magnets.
Another object of the invention is to provide a device having a lens within a sealed chamber that does not require a mechanical linkage between an internal magnet and the lens to convert the rotational movement of the internal magnet to axial movement of the lens.
A further object of the invention is to provide a device having a magnetizable lens that rotates in response to rotation of an external magnetic adjuster.
Yet another object of the invention is to provide a device that does not require an internal magnet travel within a helical channel.
Yet a further object of the invention is to provide a device with a fixed intermediate sleeve having helical grooves that provide paths for guides to travel and guide the lens in a combination of rotational and axial movement, eliminating the need to machine guide grooves or magnet seats directly into the lens.
Still another object of the invention is to provide a device that uses a magnetic field to adjust lenses without requiring both internal and external magnets.
Still another object of the invention is to provide a device having a focusing lens and zoom lenses that can be adjusted independently using separate magnetic drives.
The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.